rebuild question

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rebuild question

Postby ithomasw » Tue Dec 04, 2012 09:14 am

Hello All,

I have on my bike a SRAM Apex groupset with a compact chain set of 50 -39. matched to a 11 -32 sproket.
most of the time this is totally fine, however on weeks ride recently over some very big hills, bigger than I have ever encountered before I had to walk a lot more than I expected! ( In my defence I was carrying a bit of weight on the bike ! ) I soon realised that I needed lower gears for the touring I have started doing, so rather than go for the expensive option of a new triple chain set and levers I was planning to reduce the size of the front chain rings to 42 -27, such as an FSA comet chain set. ( I read an article in CTC mag recently on a expedition type bike that had this FSA comet chain set 42 -27.

My questions are - do I need to buy this or can I just buy smaller chain rings and fit them to the crank ?
Also would the standard SRAM apex front mech cope with this reducing or should that be changed also to such as SRAM X7 ?

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Re: rebuild question

Postby Strith » Tue Dec 04, 2012 10:24 am

Cheapest option would be to buy a 34t chainring and see how you go with that first. 34x32 should get you over anything in the uk. You should be able to find a new stronglight chainring for £10-15.
Will depend on if you're gonna carry tons of stuff, but you'll get fitter too.

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Re: rebuild question

Postby Bozman » Tue Dec 04, 2012 13:06 pm

Are you sure that the chainset is 50/39? They're usually 53/39(standard) or 50/36(compact) and a 36 - 32 combination should get you up a brick wall.

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Re: rebuild question

Postby diy » Tue Dec 04, 2012 14:10 pm

Need to check the cage capacity of your mech to be sure it can pick up the slack. Probably be ok though if it can do the big:big range already.

You seem to have some big gears already though, so maybe worth having a look at seat height/position etc, which will make a big difference to climbability.

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Re: rebuild question

Postby Monty Dog » Tue Dec 04, 2012 15:32 pm

Agree, your current chainring combination is likely to be 50/34 or 50/36 - 50/39 is pretty unusual for a stock bike.
Front mech capacity for a double is normally 16 teeth, so 42/27 is feasible with your existing mech.
If you are comfortable on your bike, I'd avoid messing with your seating / saddle position because it'll likely cause problems elsewhere e.g. dropping the saddle can create knee-tracking problems - if you want to get comfortable riding hills, simply ride more - there's no easy fix.
Make mine an Italian, with Campagnolo on the side..

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Re: rebuild question

Postby gloomyandy » Tue Dec 04, 2012 16:02 pm

So are you now using this bike as a touring bike and carrying touring style loads (panniers etc.) on it? If so then I can understand why lower gears might be a good thing. As others have said if you really do have a 50/39 then maybe try a 50/34 first? My touring bike has a mountain bike triple set on it and that has some very low gears (22 - 32!), but to be honest when things get that bad it is easier to walk! Having a triple does have other benefits though, it may mean that with a heavy load you are not having to change between the front rings so often. With a full camping setup I find I often just sit in the middle ring all day long...

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